1. Field of the Invention
The present invention relates to an image processing apparatus for imaging and recognizing an object.
2. Description of the Related Art
This type of image processing apparatus includes an image processing apparatus for recognizing a character(s) on a license plate of a vehicle such as an automobile. This image processing apparatus is referred to as a number recognition system.
For example, the number recognition system has such a structure as shown in FIG. 15, and operates according to the flow chart of FIG. 16. In this system, a single video camera 102 images a license plate 101 of, for example, an automobile stopped at a prescribed position (Step 111), and an image processing section 103 receives the resultant image to extract an image of the license plate 101 therefrom (Step 112). A determining section 104 recognizes and determines a character(s) on the extracted license plate 101 (Steps 113 and 114, respectively). Thereafter, the determined character(s) is displayed for output (Steps 115 and 116).
According to this system, it is not necessary to image the entire automobile as long as the license plate is imaged. Therefore, a stop position of the automobile with respect to the video camera is specified so that the license plate is included in the imaging field of view of the video camera.
In order to cause the automobile to be stopped at the specified stop position, it is necessary to indicate the stop position and lead the automobile thereto. In terms of simple and inexpensive construction, the stop position is clearly painted on the road so that the driver of the automobile recognizes the stop position and stops the automobile at the stop position.
In this method, however, whether or not the automobile is stopped exactly at the stop position depends on the driver""s skill. Therefore, the number recognition system must have a sufficiently large imaging range for a license plate. In the case where a small imaging range for a license plate is set, the license plate would not be imaged if the automobile is stopped at a position away from the specified stop position. Therefore, the number recognition system does not perform its proper function.
According to the number recognition system, the stop position of the automobile must be limited in some way. In many cases, the license plate is imaged by a single video camera, making the imaging range for the license plate extremely small. Therefore, the margin for error in an actual stop position of the automobile is small.
Moreover, automobiles of different types have different sizes, and different license plate positions. Accordingly, even if the automobile can be stopped at the specified position, the position of the license plate can not always be accurately determined. As a result, the imaging range of the video camera must be carefully determined.
For the system user, it is preferable that the stop position of the automobile is less critical. In other words, it is more convenient for the system user to stop the automobile at an arbitrary position. Therefore, the conventional number recognition system is less preferable.
Furthermore, it is preferable for the system to have a large imaging range of the video camera in terms of the degree of freedom in system design and installation.
As described above, in the case where the license plate is imaged by a single video camera, the imaging range for the license plate is very small. Therefore, the stop position of the automobile is limited and the degree of freedom in system design and installation is reduced, making the system less advantageous.
A high-resolution video camera having a large imaging range has been proposed to ensure character recognition on the license plate with a less-limited stop position of the automobile. Moreover, Japanese Laid-open Publication No. 7-105352 describes an xe2x80x9cimage processing apparatusxe2x80x9d including two video cameras having different imaging ranges, wherein the respective images obtained by the video cameras are processed.
However, the high-resolution video camera having a large field of view is expensive. Furthermore, a large amount of data is produced in order to obtain an image, increasing the image processing time, and thus, the extraction time of the license plate. Moreover, in the case where a larger field of view is required, a higher-resolution imaging device is required, thereby further increasing the image processing time.
Moreover, in the case where two video cameras having respective imaging ranges are used as described in Japanese Laid-open Publication No. 7-105352, the imaging ranges must be adjusted upon system installation so that the imaging ranges are adjacent to each other. Such adjustment is largely affected by the conditions of the installation location and the skill of a person who installs the system, causing a divergence of the system reliability and an increase in the processing steps. Furthermore, since the relative positions of the imaging ranges of the video cameras are changed according to the installation conditions, a software for processing the images obtained by the video cameras must be adjusted according to the installation conditions.
According to one aspect of the present invention, an image processing apparatus includes a plurality of imaging devices located at respective prescribed positions; at least one optical device for receiving light and projecting an image of the received light to the imaging devices; and an image processing section for processing respective images obtained by the imaging devices, wherein the imaging devices and the optical section form a single unit.
In one example, the optical device is a single element, and projects an entire image to imaging screens of the plurality of imaging devices.
In one example, an image processing apparatus further includes a semi-transparent mirror for dividing light from the optical device into a plurality of portions to assign respective images of the divided portions of light to the respective imaging devices.
In one example, an image processing apparatus further includes a detecting section for detecting a position of an object, wherein the image processing section selects one of the respective images obtained by the imaging devices, based on the detected position of the object, and processes the selected image.
In one example, the image processing section extracts the object from the selected image.
In one example, the image processing section synthesizes at least two of the respective images obtained by the imaging devices into a single image having no overlapping portion.
In one example, the image processing section extracts the object from the single image resulting from synthesizing at least two of the respective images obtained by the imaging devices.
According to the present invention, since the imaging devices and the optical device(s) form a single unit, the relative positions of the imaging ranges of the imaging devices are specified. Therefore, the respective imaging ranges of the imaging devices need not be adjusted upon installation of the image processing apparatus, whereby the image processing apparatus can be easily installed with increased reliability. Moreover, since the relative positions of the imaging ranges of the imaging devices are specified, the process conducted by the image processing section can be determined in advance. Therefore, an image processing software need not be adjusted upon installation of the image processing apparatus. It should be understood that a large imaging range can be ensured by pre-setting the imaging ranges of the plurality of imaging devices as appropriate.
By detecting the object position, and selecting one of the respective images obtained by the imaging devices according to the detected object position, the image of the imaging device capturing the object can be selected with a high probability. As a result, the image including the object can be quickly processed.
Thus, the invention described herein makes possible the advantage of providing an image processing apparatus having a large imaging range, capable of being easily installed without degrading its operation capability and reliability, and also capable of reducing the cost.
This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.